This invention relates generally to computers and computer software, and more specifically to a virtual replication system and method for a distributed data network.
Personal computers or workstations may be linked in a computer network to facilitate the sharing of data, applications, files, and other resources. One common type of computer network is a client/server network, where some computers act as servers and others as clients. In a client/server network, the sharing of resources is accomplished through the use of one or more servers. Each server includes a processing unit that is dedicated to managing centralized resources and to sharing these resources with other servers and/or various personal computers and workstations, which are known as the xe2x80x9cclientsxe2x80x9d of the server.
Directories and directory services are often provided to enable a digital environment for a particular resource. One example of a directory service is Novell Directory Services (xe2x80x9cNDSxe2x80x9d) for Novell Netware networks, as provided by Novell, Inc. of Provo, Utah. NDS provides a logical tree-structure view of all resources on the network so that clients can access them without knowing where they are physically located. For a given resource, an entry is made in a directory such as NDS. Specific entries of a directory are only available by directly accessing the directory.
Typically, applications operate against a single, non-distributed directory to access information that is pertinent to the application. In this manner the application can access all of the information it needs from this single source. From an administrative perspective, this presents a problem since the information is stored on an application by application basis and the administrator is forced to often manage duplicate sets of data stored in multiple locations
To solve this administrative problem, distributed directory environments such as NDS, have been developed to allow for the partitioning of the data into sets that given applications may be interested in, then distributing copies of these sets to where these applications can locally access them. The separate copies, or Replicas, are kept current through an automated process called Replication. In this manner administrators can place specific information where it is most needed, yet are still able to centrally manage this information.
However, distribution of this data brings its own set of problems. For instance, if the set of information that is of interest to a given application spans the entire distributed network, the application would have to either maintain a local replica of all of the sets of data in the network or would be forced to remotely access replicas of the sets of data that do not reside locally. Either solution is undesirable. Maintaining a local replica of all of the data sets would require a lot more storage capacity and network bandwidth, and much of the data that would be stored and replicated would not be of interest to the application. Remotely accessing nonlocal sets of data would be slow and there would be a chance that the application may not be able to access all of the data it needs all of the time.
It is desired to have a distributed directory maintained such that multiple applications could use it as though they were working on a single, centralized directory.
It is also desired to be able to filter out subsets of data from a given replica in order to allow for the storage of only the data that is of interest to a given application and to reduce the amount of network traffic caused by replication events in a distributed data environment.
In response to these and other problems, an improved system, method and software program is provided for facilitating the use of components running in a computer network. To this end, the improvement provides virtual replication of a distributed directory in a computer system. The system includes at least two servers, each including a processor connected to a network for executing computer code, and a memory system. The memory of the first server can store, among other things, a partition of information. In some embodiments, the partition may be distributed across the network. The memory of the second server can store, among other things, a virtual replica of the partition. The virtual replica includes a filtered view, or subset, of the information in the partition.
In some embodiments, the virtual replica provides an application using the second server with a centralized copy of specific information from the directory in which the application is interested (the filtered view). The application can then access all of the information that it needs via a local read to the second server. Also, with certain replication technology, such as is found in NDS directories, the virtual replica can be dynamically updated as modifications are made elsewhere in the directory.
In some embodiments, the second server also includes an inbound replication software process for receiving events from the partition and then filtering the events according to the filtered view.
In some embodiments, the first server includes an outbound replication software process for filtering events from the partition and transferring the filtered events to the virtual replica.
An advantage of the present invention is that most of the difficulties that arise when applications have to access a distributed directory are reduced and/or eliminated.
Other advantages can be readily seen by further examination of the attached figures and the following description.